(A) Representative responses to 1, 3, 10, 30, and 100 mM lidocaine of HEK293t cells transiently expressing rTRPV1. The holding potential (V_h) was –60 mV. Various concentrations of lidocaine were applied for about 10 s. Only 1 concentration per cell was applied. (B) Concentration-response curve for lidocaine. Each data point represents mean peak current amplitudes evoked by 1, 3, 10, 30, or 100 mM lidocaine in 11 independent cells each. The line represents a fit of the data to the Hill equation. (C) Outward currents evoked by 3, 10, and 30 mM lidocaine in a HEK293t cell held at +60 mV. Lidocaine was applied for about 10 s in intervals of 2 min. (D) Representative ramp currents of TRPV1 in control solution, in 30 mM lidocaine, and in 30 nM capsaicin (n = 8). Cells were held at –60 mV, and currents were measured during 500-ms-long voltage ramps from –100 to +100 mV. Note the typical outward rectification of TRPV1 at 30 mM lidocaine and 30 nM capsaicin. (E) Representative capsaicin-evoked inward currents blocked by lidocaine. Increasing concentrations of lidocaine were coapplied with capsaicin after currents were evoked by a supramaximal concentration of capsaicin (10 μM). Cells were held at –60 mV, and experiments were performed in a Ca²⁺-free extracellular solution in order to avoid desensitization. (F) Dose-response curve for lidocaine-induced block of TRPV1 inward (V_h, –60 mV) and outward (V_h, +60 mV) currents evoked by capsaicin. The fractional block was plotted against the lidocaine concentration. Lines represent fits of the data to the Hill equation. The IC₅₀ values were 45 ± 7 mM (n = 4) at –60 mV and 16 ± 17 mM (n = 4) at +60 mV. (G–I) Effect of the noncompetitive TRPV1 antagonist ruthenium red (RR, 5 μM; G), the competitive TRPV1 antagonist capsazepine (CPZ, 10 μM; H), and the highly selective TRPV1 antagonist BCTC (100 nM; I) on lidocaine-evoked currents in HEK293t cells expressing TRPV1. The substances were coapplied with 15 mM lidocaine after currents evoked by 15 mM lidocaine had reached steady state.